Wetness indicators especially on diapers and incontinence guards for adult incontinent persons, have been known for several years and facilitates for the nursing staff to determine whether the diaper or incontinence guard needs to be changed. It for example known through EP-A-0 211 524 to print a pattern of a water soluble dye on the inside of the back sheet material of a diaper by means of ink beam technique. The dyestuff can alternatively be of a type that changes color or tint when brought into contact with urine. The printed pattern can also consist of symbols or codes for quality- or other manufacturing control.
It is further known through EP-A-0 203 715 to treat an absorbent body of a diaper so that it gets a tight paper like structure on the backside, which then is used as a reception surface for a wetness indicating dye applied in a pattern that is visible through the backside material of the diaper.
It is also known to have capillary wetness indicators, i.e., a thin strip or thread having a high capillary effect arranged in connection to the absorption body and which is in contact with an indicator which dissolves, changes color or tint when brought in contact with a liquid. Such wetness indicators are known through for example U.S. Pat. No. 4,738,674 and GB-A-2 327 354.
The wetness indicator can be arranged at different locations, such as along the side of the absorption body or on the underside thereof. It can be therefore be difficult for the nurse to locate the wetness indicator on the article in order to read it to see whether the article needs to be changed or not.
WO 99/16401 discloses an diaper having a wetness indicator on the inside of the back sheet material. The back sheet material is a laminate of a fibrous nonwoven material and a polymer sheet. A plurality of translucent windows are arranged in said back sheet through which the wetness indicator is visible.
U.S. Pat. No. 4,231,370 discloses a diaper having a wetness indicator in the form of a coating applied in a pattern on the inside of a translucent back sheet material.
FR-A-2 711 317 discloses a wetness indicator comprising an inner portion which changes color when it is wetted by urine and an outer portion which is translucent plastic material.
EP-A-0 925 769 discloses a diaper having a back sheet with transparent zones through which a wetness of the absorbent core can be observed.